The present invention is a motion and position sensor which can be used as an electronic drum, much like an electronic keyboard is used with a musical synthesizer. The present invention can also be used for inputting one-dimensional, two-dimensional or three-dimensional data points into a computer of any other system.
The present invention uses a capacitive two dimensional tablet which is similar in some respects to the digitizer described in U.S. Pat. No. 4,705,919, and the capacitive two dimensional tables shown in U.S. Pat. Nos. 3,999,012 and 4,087,625. The present invention is an improvement on these prior art devices in that it detects the Z coordinate of a baton or stylus, corresponding to the height of the baton or stylus over a surface, as well as the X and Y coordinates of the baton or stylus. An additional improvement over the prior art is that the signals used in the present invention to determine the X coordinate are completely separate from the signals used to determine the Y coordinate, which simplifies the calculations and improves the accuracy of the X and Y coordinates.
In prior art motion and position sensors, there is a time lag between the motion of the stylus or baton being used, and the generation of the corresponding signals. This is acceptable for many applications, but is not acceptable when the baton is being used with a musical synthesizer to control when certain musical sounds are generated.
The present invention has advantages in terms of the accuracy of the X and Y coordinate data that it generates, and also in that it uses a predictive method of determining when a baton will hit a surface. This is particularly useful in musical applications, where it is important that the generation of a drum beat or other musical event be accurately synchronized with a drum player's hand motions.
Another object of the present invention is to provide a motion or position sensor that can simultaneously detect the positions to two or more batons. Once again this is particularly useful in musical applications, where a drum player will typically use two drum sticks, and may use more than two sticks.